1. Field of the Invention
The present invention relates to a throttle body which controls air flow supplied to an engine in the fuel injection apparatus, and more particularly, relates to a throttle control apparatus used for a motorcycle.
2. Description of the Conventional Art
A conventional throttle body will be described below with reference to FIG. 2 which is a longitudinal section of the throttle body.
In FIG. 2, the reference numeral 10 indicates a throttle body having an intake passage 11 extending through laterally therein. A throttle valve shaft 12 is provided across the intake passage 11, and both ends of the throttle valve shaft 12 are rotatably supported on the throttle body 10.
Also, a throttle valve 13 is provided in the intake passage 11 for opening or closing the intake passage 11. The throttle valve 13 is mounted on the throttle valve shaft 12 so as to open or close the intake passage 11 in response to the rotation of the throttle valve shaft 12.
Another end 12a of the throttle valve shaft 12 is protruded rightward from an another side outer wall 10a of the throttle body 10 (right side as shown in FIG. 2), and a drive lever 14 is mounted integrally with the other end 12a. 
The reference numeral 15 indicates a rotary shaft provided uprightly on the other side outer wall 10a of the throttle body 10. A throttle lever 16 is fixed to the rotary shaft 15 by means of a screw nut.
One end of an accelerator wire (not shown) for opening the throttle valve 13 and one end of an accelerator wire (not shown) for closing the throttle valve 13 are retained to the throttle lever 16, and other ends of the accelerator wires are connected to an acceleration grip, respectively.
When the acceleration grip is rotated by a driver, this rotation is transmitted to the throttle lever 16 through the accelerator wire to rotate the throttle lever 16 in response to the rotation of the acceleration grip.
The reference numeral 17 indicates a link lever which connects the throttle lever 16 and the drive lever 14. The rotation of the throttle lever 16 is transmitted to the drive lever 14 through the link lever 17. Due to the arrangement where the throttle lever 16 and the drive lever 14 are connected by means of the link lever 17, the rotation of the acceleration grip and the opening characteristic of the throttle valve 13 are made nonlinear.
Like this, a throttle lever mechanism T comprising the throttle lever 16, link lever 17 and drive lever 14 is mounted to the end 12a of the throttle valve shaft 12.
Also, a lever accommodation wall 10e is integrally formed with the other side outer wall 10a of the throttle body 10 to surround the periphery of the throttle lever mechanism T including the other end 12a of the throttle valve shaft 12, and right side opening portion 10c of the lever accommodation wall 10e is closed by a cover 18.
The throttle lever mechanism T is disposed in the accommodation space defined by the a lever accommodation wall 10e and the cover 18 so that the throttle lever mechanism T is protected against the outer obstacles or against splash of muddy water when the throttle body 10 is installed on such a portion of the motor cycle as directly exposed to the outside air.
The reference numeral 19 indicates a throttle opening sensor mounted to one end 12b of the throttle valve shaft 12 which protrudes from one side outer wall 10d of the throttle body 10. The output signal from the opening sensor 19 is inputted to ECU (not shown) and is used for the various control.
According to such conventional throttle control apparatus, the throttle lever mechanism T comprising the throttle lever 16, link lever 17 and drive lever 14 is attached to the other side outer wall 10a of the throttle body 10, and the cover 18 is attached to the opening portion 10c of the lever accommodation wall 10e, while the opening sensor 19 is mounted to the one end 12b of the throttle valve shaft 12 supported on the one side outer wall 10d of the throttle body 10.
With such structure, since assembling of the throttle lever mechanism and the opening sensor with the throttle body has to be carried out from the opposite directions, it is difficult to perform an efficient assembling operation
Further, when maintenance work of the throttle lever mechanism T and the opening sensor 19 is done in a state where the throttle body is installed on the motorcycle, the working has to be done from the different directions, resulting in poor workability.
Furthermore, in the conventional throttle control apparatus, since the drive lever 14 is mounted to the other end 12a of the throttle valve shaft 12, a flat portion 12c is formed at the other end 12a so that the drive lever 14 is prevented from being rotated against the throttle valve shaft 12, while, since a flat groove of the opening sensor 19 is retained to the one end 12b of the throttle valve shaft 12, a flat portion 12d is formed at the one end 12b of the throttle valve shaft 12.
In the machining of the throttle shaft 12 which is made of hard steel such as cutting steel, one flat portion 12c is formed at the other end 12a of the throttle valve shaft 12, then the shaft 12 is reversed in position, and another flat portion 12d is formed at the one end 12b of the shaft 12, resulting in a difficulty of reducing the manufacturing cost of the throttle valve shaft 12.
Further, in the conventional throttle control apparatus, the lead wire of the opening sensor 19 is disposed at the side of the one side outer wall 10d of the throttle body 10, while the accelerator wire is disposed at the side of the other side outer wall 10a of the throttle body 10, i.e. the lead wire and accelerator wire are disposed astride the intake passage 11 of the throttle body 10. Thus, it is difficult to connect the wires for the motorcycle where the throttle body is disposed in a narrow space under a driver's seat.